Overheating false Alarm??

[crappiejigger]

Okay guys ive got a Ranger R72 with a Mercury 115HP outboard #OG101672. The problem im having is about a year ago me and my son was out fishing when i got a high temp alarm out of the blue.It kinded sounded faint and like it was cutting in and out on sound (was a constant on beep)So i shut off engine and let it cool. i fished a while as i waited but every time i turned over key alarm was going? i attempted to start engine to get cooling water flowing, I then got up on plane to get back to ramp due to storm brooing after i got up on plane the alarm cut in and out like there was a bad connection. i ended up changing out the waterpump thinking that would solve my problem.Now after changing waterpump last year i still get every once in a while out of the blue a constant beep alarm. Here most recent I unloaded the boat motored out of marina and before I could get up on plane the overheat alarm started going off. This is with engine running maybe ten minutes, so i motored over to my first spot and shut off engine. I decided to fish stretch of bank that took approx. 1 1/2 hours to fish, meanwhile checking ever so often if alarm would clear. Every time i checked the alarm was still activated for overtemp? After the hour and a half passed i knew there was no way the engine overheated that bad after running for less than 10minutes. so i did some on the water surgery, i pulled the temp alarm sensor from block and it was cold to the touch as was the engine in several spots.Needless to say while doing this i had key turned over and the constant beep stayed on. So i knew i had a false alarm? I figured i had a bad sensor so i turned off key pulled screw that held temp sensor electrical connection to side of engine with two other wires then reinstalled screw with the other wires and left temp sensor electrical connection disconnected.when i turned over key the constant beep alarm was still going off???? I started engine and motored around with alarm going off then it cut in and out than stopped. didnt have issue with it the rest of the short day. So i figure Ive got a wire going to ground that is causing false alarm because alarm was going off with temp sensor disconnected right? while it was going off also i tied wiggleing the wires under dash and around ignition switch to see if i could find a wire that would cause it to stop(no luck). Than today in driveway i tried wiggling wire to see if i could get alarm to go off with no luck? so im at a loss of what to do next any suggestions of what this could be? I was thinking maybe short in my key/ignition switch but just guessing? any ideas would greatly be appreciated- Also i reconnected temp sensor since i figure it isnt the cause.

[11pounder]

Could it be the low oil alarm?

[crappiejigger]

I don't believe so, when it comes on its constant. I'm pretty sure it's the high temp.

[6BOOMER]

http://www.bbcboards.net/showthread.php?t=528835

[SilverFox579]

I don't know the alarm strategy on your engine, but, are you absolutely certain the only critical alarm indication (solid tone) is for overheat? I suspect there are other critical alarm conditions that will trigger a solid tone.

[11pounder]

The low oil alarm is solid, and if the float in the engine mounted tank becomes saturated it will sink to the bottom of the tank and give you an alarm even though the tank is full.

[Dean Evans]

Low oil is an intermitten or broken alarm on this model. some where you are getting a ground interference to alarm could be temp sensor, cracked wire from sensor or warning module or boat or engine harness. disconnect heat sensor from connector at warning module and engine harness hook module and heat sensor one at a time to engine harness with key on and see if one or the other will set off alarm

[EuropeanAM]

Check the tan w/blue stripe wire running from the temp sensor for any nicks, melted spots, etc. Anything that provides a ground on this wire will result in the horn sounding.

[crappiejigger]

Yea I've tried find bare wire,but no luck, also tried wiggling all the wires while key was turned over to listen for any indication of the horn no luck. I might pull throttle control lever and check there?? So am I right in saying on this motor a solid horn is a overheat warning?? Been on twelves so haven't been able to mess with or look in manual for horn meanings.

[Lowerider58]

Yea I've tried find bare wire,but no luck, also tried wiggling all the wires while key was turned over to listen for any indication of the horn no luck. I might pull throttle control lever and check there?? So am I right in saying on this motor a solid horn is a overheat warning?? Been on twelves so haven't been able to mess with or look in manual for horn meanings.

It's not just for overheat. Refer to the link in post #4.

[crappiejigger]

Yes lowrider I seen post #4, but I looked at my motors owner manual and it specifically states solid tone is the overheat warning. This is I believe a 95 mercury 115hp. The problem is im randomly getting overheat alarm when it's not overheated? Had it out the past two days, with no real issue except the first day running back to marina and just outside of marina the alarm started to sound as I slowed down it sort of cut out (horn) and never heard a peep out of it again.im going to have to investigate more, wondering if the wire for overheat alarm goes through throttle box and possibly has been rubbed bare inside it. But horn sound seems to be coming out of ignition switch on dash?? If I find something I'll keep ya guys posted.

[kneelnreel]

sensor is bad just went thou this same thing with mine replaced sensor prob gone

[EuropeanAM]

Yes lowrider I seen post #4, but I looked at my motors owner manual and it specifically states solid tone is the overheat warning. This is I believe a 95 mercury 115hp. The problem is im randomly getting overheat alarm when it's not overheated? Had it out the past two days, with no real issue except the first day running back to marina and just outside of marina the alarm started to sound as I slowed down it sort of cut out (horn) and never heard a peep out of it again.im going to have to investigate more, wondering if the wire for overheat alarm goes through throttle box and possibly has been rubbed bare inside it. But horn sound seems to be coming out of ignition switch on dash?? If I find something I'll keep ya guys posted.

How are you determining (specifically) that the engine is not overheating? (As in what evidence are you using to come to that conclusion)

[crappiejigger]

Well the alarm went off after 10 minutes of running, so I shut off to fish. Kept turning over key to check if alarm cleared,but stayed on for approx an 1 1/2 hrs. So I got curious and pulled hood and pulled out sensor from hole. It was ambient in temp and engine was barely warm everywhere I touched. Even with sensor out of block alarm was going off? So I figured I had a bad sensor so I unbolted it where it is bolted to side of engine. Turned over key and still had a solid tone alarm, even with sensor completely disconnected??? So I ran engine a little and alarm finally quit? Later I hooked back up sensor just in case but can't figure out why I'm getting this alarm every once in a while, assuming I got a bare wire some where going to ground just can't find.

[EuropeanAM]

I know you said this was a "constant" alarm.... but let's be 110% sure:


SOLID TONE "BEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE EEEEEEEEEEEEP"

and NOT a FAST BEEPING, correct?

[crappiejigger]

Yes a long solid beeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep. Had it out recently and it started to sound but sounded like it was curing in and out like a bad connection than came on constant for about 30 sec to maybe a minute then went silent again? I can't figure it out tried wiggling wires to try and find it, tried tapping on little horn under dash to see if it's got something loose but know luck?? I will say this now I've went and screwed something up with my tachometer cause now it's not working? So I've actually made things worse!! That's my luck

[JOE54]

you can eliminate the oil tank question by unplugging light blue wires from connectors if it still has horn sound not gona be tank and float related/ be sure to check poppet and thermostat for sticking and operation located top of plate on back of block/remote key switch and harness 1500a7 will eliminate boat wiring as culprit

[sooner magic]

I don't know alot about Merc's but I recently bought one and I was having the same problem even down to the tach screwing up and mine turned out tobe the low oil alarm. I couldn't belive it because the oil tank still had over a 1/4 left in it. A buddy told me when it's that low it will do that on my motor (2002 ELPTO Ser.#OT527309). Since I started keeping the oil tank full no more alarm or weird tach. Coincidence, maybe but it worked for me. Good luck and keep us informed.

[qmanfishing]

Impeller ... and make sure they replace the housing because the housing starts to melt together and restrict flow... long idles worsen the condition ..... had an old one I used to half to replace twice a year